Recovering solvent from process steam



Oct; 13, 1953 R. L. GREENE RECOVERING SOLVENT FROM PROCESS STEAM Filed March 10, 1951 law 3 600 E II.

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Patented Oct. 13, 19s3 2,655,468

UNITED STATES PATENT OFFICE RECOVERING SOLVENT FROM PROCESS STEAM Robert L. Greene, Westfield, N. J., assignor to Standard Oil Development Company, a corporation of Delaware Application March 10, 1951, Serial No. 214,894

4 Claims. (Cl. 20242) The present invention relates to a process for tank 7 and passed by line 8 to extraction zone 9 the solvent extraction of lubricating oils and The phenol-cresol mixture flows through the more partlcularly relates the recovery of system from extraction zone 6 to extraction zone vent from the steam used in stripping the extract r 3 by line H and to extraction zone 9 by line I2 and raffinate streams. and 1s finally withdi awn from extraction zone 9 r ces s pr pan is empl yed as a para 10 through line It. The phenol-cresol mixture stock- The p opa e ayer carries he stable layer. The extract layer is contacted with an;

Steam Stripping the mixture of Phenol and comes into contact with a more and more concresol in a low pressure towerh water is centrated solution of phenol-cresol, thus being customarily separa d f m h phenol-crest)! stripped of its asphaltic oil content. Separation mixture by whereby a constant boil- 0f the two layers in each extra t on one 15 ing mixture of steam and phenol-cresol is taken accomplished by gravity overhead and substantially water-free phenol- Th rafiinate flowing through line I6 is passed eresol is ta n OIT as o The azeotlope to the top of tower I 7 where it is distilled under m high pressure to remove pure propane overhead in a 0118 Stage extractor W h quid propane to W through line l8. I'his propane is passed by line of solvent. to tower 2! where it is similarly distilled under It is the main object of the presentinvention high pressure t bt i propane verhe d to pr vid a m d for recovering D S Steam through line 22 which is recycled to the propane Which s Sub y free of Solvent 40 tank 1 through line IS. The bottoms from tower description and the annexed drawing setting extract phases they are submitted to steam Referring now to the drawing, a lubricating bottom of tower 24 through line 26 and to the oil stock is drawn from tank I and passed by bottom of tower 25 through line 21. Rafiinate line 2 to intermediate extraction zone 3. A mixis removed at 600 F. from tower 24 through line ture of 60% phenol and 40% mixed cresols is 46 and passed to exchanger 4|. Extract is rewithdrawn from tank 4 and passed by line 5 to moved at 600 F. from tower 25 through line 41"; extraction zone 6. Propane is withdrawn from and passedtoexchanger 42.

The overhead from each of towers 24 and 25 consists of steam and the phenol-cresol present in the respective raflinate and extract streams. The overhead from tower 24 is removed through line 28 and that from tower 25 through line 29. These streams are combined and cooled in condenser 30 and passed to the bottom or water evaporator 31 from which an azeotropic mixture of 90% steam and 10% phenol-cresol is taken overhead through line 32. An anhydrous mix-- ture of phenol and cresol is removed from the bottom of tower 3| by line '33 and returned to storage tank 4. The azeotrope flowing in line 32 is condensed in cooler 34 and passed to water reflux tank 35 from which reflux is returned to the tower 3| through line 36. The remainder of the condensate in tank 35 is passed by line 31 to propane line 19 where it is mixed with the propane and passed to storage tank I. The

propane acts to break the azeotrope and forms two layers, a, water layer'on the bottom, still containing about 1-*3% phenol-cresol mixture and propane containing a small amount of phenol-cresol on top. This latter layer remains and is recycled to the system as the propane solvent. The water layer is withdrawn through line 93 and passed to the top of an azeotrope tower 39 from which substantially pure water is taken off the bottom through line 40 and passed to raffinate and extract heat exchangers 4| and 42 in which the water is converted to steam. This steam is passed byline 43 to steam superheater 44 and recycled to the system through line 45-.

The overhead from azeotro'pe tower 39 is an azeotropic mixture of 92-96% water and 4-8% phenol -cresol mixture and is passed by line 46 to condenser 31} where it iscondensed along with the overhead from tower 31. Thus naphthenic solvent substantially free of water is removed from the bottom of tower '31 and water substantially free f naphth'eni'c solve t (0.1%) from tower 39. By this process the loss or solvent is maintained at a minimum and the steam circulated through the system is of a better quality.

The nature or the present i'r'ivetion having been thus fully set iortha'nd specific examples of the same given, what is claimed as newand useful and desired to be secured by Letters Patht is:

1. 111 the extraction or lubricating oil stocks by means of two immiscible solvents, a first solvent for the parafiinic constituents and a second solvent for the naphthenic constituents wherein said first solvent is removed from the raffinate and extract fractions by distillation and said second solvent is then removed from the raffinate and extract fractions by stripping them with steam, wherein the stream of steam and saicl sec- 0nd solvent from the stripping operation are fractionated to form a first overhead azeotropic traction comprising steam and said second solvent,

the improvement which comprises in combination condensing said first overhead azeotropic fraction, contacting the resulting condensate with said first solvent whereby a portion of said second solvent is extracted from said condensed first azeotropic fraction, iractionating the resulting raifinate to form a second overhead azeotropic fraction comprising steam and said second solvent and a bottoms fraction comprising substantially pure water and recycling said secand overhead azeotropic fraction by blending it with "said first overhead azeotropic fraction.

2. A process as defined in claim 1 in which at least a portion of the bottoms fraction comprismg substantially pure water is vaporized and recycled to the stripping operations.

3. The extraction of lubricating oil stocks by means of two substantially immiscible solvents comprising propane and a mixture oi phenol and cresol, wherein the propane is removed from the rafiinate and extract fractions by distillation and the phenol-cresol mixture is then removed from the same fractions by stripping them with steam, wherein the stream of steam and the phenolcresol mixture from the stripping operations is condensed and fractionated to form a first overhead azeotropic fraction comprising steam and a mixture of phenol and cresol and a bottoms fraction comprising a substantially pure mixture of phenol and cresol, the improvement which comprises condensing said first overhead azeocontacting the resulting con densate with liquid propane whereby a portion of the phenol-cresol mixture is extracted from said condensed first azeotropic fraction, fractionating the resulting rafilnate to form a second overhead azeotropic fraction comprising steam and a mixture of phenol and cresol and a bottoms fraction comprising substantially pure water and recycling said second overhead azeo tropic fraction by blending it with said first overhead azeotropic fraction w 4. A process as defined in claim 3, in which at least a portion of the bottoms fraction of sub stantially pure water is vaporized and recycled to the stripping opera 'ons, e v

ROBERT L.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Re. 19,*763 Tuttle -e- Nov. 19, 1935 1,373,901 Miller Aug. 23, 1932 1,912,349 Tuttle -1- May 30, 1933 2,111,822 Sullivan Mar. 22, 1938 2,177,183 Kraft Oct. 24, 1939 2,289,056 Brown June 9, 194 2 2,303,023 C161" Nov. 24, 1942 2,307,242 seven Jan. 5, 1943 2,322,881 Pollock June 29, 1943 

1. IN THE EXTRACTION OF LUBRICATING OIL STOCKS BY MEANS OF TWO IMMISCIBLE SOLVENTS, A FIRST SOLVENT FOR THE PARAFFINIC CONSTITUENTS AND A SECOND SOLVENT FOR THE NAPHTHENIC CONSTITUENTS WHEREIN SAID FIRST SOLVENT IS REMOVED FROM THE RAFFINATE AND EXTRACT FRACTIONS BY DISTILLATION AND SAID SECOND SOLVENT IS THEN REMOVED FROM THE RAFFINATE AND EXTRACT FRACTIONS BY STRIPPING THEM WITH STEAM, WHEREIN THE STREAM OF STEAM AND SAID SECOND SOLVENT FROM THE STRIPPING OPERATION ARE FRACTIONATED TO FORM A FIRST OVERHEAD AZEOTROPIC FRACTION COMPRISING STEAM AND SAID SECOND SOLVENT, THE IMPROVEMENT WHICH COMPRISES IN COMBINATION CONDENSING SAID FIRST OVERHEAD AZEOTROPIC FRACTION, CONTACTING THE RESULTING CONDENSATE WITH SAID FIRST SOLVENT WHEREBY A PORTION OF SAID SECOND SOLVENT IS EXTRACTED FROM SAID CONDENSED FIRST AZEOTROPIC FRACTION, FRACTIONATING THE RESULTING RAFFINATE TO FORM A SECOND OVERHEAT AZEOTROPIC FRACTION COMPRISING STEAM AND SAID SECOND SOLVENT AND A BOTTOMS FRACTION COMPRISING SUBSTANTIALLY PURE WATER AND RECYCLING SAID SECOND OVERHEAD AZEOTROPIC FRACTION BY BLENDING IT WITH SAID FIRST OVERHEAD AZEOTROPIC FRACTION. 